Harlequin fish
| Harlequin fish | |
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| Genus: | Othos Castelnau, 1875
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| Species: | O. dentex (Cuvier in Cuvier and Valenciennes, 1828)
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| Binomial name | |
| Othos dentex | |
Othos dentex is a species of fish in the family Serranidae. It is the only member of the genus Othos. It is known commonly as the harlequin fish.[1] This species is found in the Eastern Indian Ocean and is endemic to Australian waters.[2]
Description
O. dentex is one of the largest serranids in the Southern Australian water, is a diurnal forager that has a long life-cycle, and has a small home range and strong side fidelity[3][4]. It is likely to be harmed by localized anthropogenic changes[5] and by recreational fishing, though their fishing along the coast is low[3].
Anatomy
Physical Appearance
O. dentex has a heterogeneous color pattern that varies from individual to individual, which blends with the colors and surrounding coralline algea and encrusting sponges in the reef, providing a camouflage for them[3]. The color variation, between individuals, is due to the large blotches which range from yellow to green [6] that are located posterior to the pectoral fin on the lower half of the body[3]. While all individuals have longitudinal blue flecks on the dorsal surface of the body, as males become mature these flecks become more prominent, and their spots change from yellow to green and finally, once they reach full maturity, to blue[3].
During spawning season, the color of blotches in males intensify, peaking at intensity during the mid-point of the season, which plays a role in courtship[3]. This color change also suggests a change in their androgen levels[7][8]. O. dentex has independently movable eyes that protrude on top of its head[9], and a large sized mouth.
Mouth and Dentition
The anterior upper jaw of O. dentex contain two pairs of closely-apposed big, recurved and pointed canines. Numerous, inwardly-directed, very small pointed teeth extend backwards, in rows and declining in size, from the large canines on the margins of both sides of the upper jaw. Two large recurved and elongated canines sit anteriorly in the lower jaw, on either side, and three teeth, similar in shape, are further back. Their gill rakers have backwards-pointing spines.[5]
Life Cycle
O. dentex can live up 42 years[10], and can grow a maximum length of 75 cm[11][12]. In the otoliths of O. dentex, a single opaque zone forms annually, and age of the individual can be determined by the number of these zones[3]. Considering their long life at the young age of 4-5, both the females and males, grow rapidly[3], with the males showing slight change in color as they reach maturity. Before maturing, the early juveniles are thought to be residing in the crannies and deeper in the caves, which would protect them against predatory piscivorous fish species that exist nearby[13]. As the juvenile individuals approach their mature size, they start moving around the reef. Typically, the male individuals are solitary, and come together with females during spawning season[3].
Sexual Reproduction
O. dentex is a gonochorist species, it has indeterminate fecundity.This species also exhibits batch spawning which corresponds with the individuals being widely dispersed and scarce[14][5]. It’s unknown whether juveniles present bisexuality early in life, but if bisexuality is present, it’s assumed that, some time before the individual reaches maturity, it disappears early in gonadal development[3]. Unlike other gonochoristic members of Serranidae, O. dentex have small testes, which implies low sperm competition[15][16]. The spawning season for O. dentex is through September to March, and it peaks during the period between November and January[3]. Indeterminate fecundity over the long life span as well as its long-lasting spawning period play a key role in egg and larval survival. These factors guarantee that of the numerous eggs that were produced during the spawning season majority of them will be released at a time that’s favorable for the egg and larval[17].
Ecology
Distribution and Habitat:
O. Dentex is native to the temperate waters, and is found over the shallow rocky reefs and in caves located in the cool coast of South-Western Australian waters[3][8]. It’s believed that this reef-dwelling species has an important place in the ecology of its environment since it is a top predator, and is relatively common in the area[5].
Diet
O. dentex is a demersal piscivore, and feeds during daylight. Its mature individuals feed exclusively on fish, and their prey, which is selected for on the basis of their size rather than species, and include species of teleosts, like the Labridae and the Pempheridae[9]. Because juveniles would be unable to ingest prey as large as fishes, its assumed that they feed on other species besides teleosts[5]. O. dentex feeds intermittently and its dietary composition lacks seasonality. When this diurnally active species is looking for food, it usually will lie over hard structures and wait for a prey, and when the prey is within range it will dart forward to attack its prey[9]. Its physical appearance as well as the anatomy of its protruding eyes help with its foraging success [18][19].
References
- ^ Othos dentax in ITIS
- ^ Fishbase.se
- ^ a b c d e f g h i j k l French, B., Potter, I. C., Hesp, S. A., Coulson, P. G. and Hall, N. G. (2014), Biology of the harlequin fish Othos dentex (Serranidae), with particular emphasis on sexual pattern and other reproductive characteristics. J Fish Biol, 84: 106-132
- ^ Bryars, S. & Rogers, P. J. (2016). Movements in the harlequin fish (Othos dentex), a large predatory serranid from southern Australia: implications for detection and protection. New Zealand Journal of Marine and Freshwater Research 50, 600–618
- ^ a b c d e French, B., Platell, M. E., Clarke, K. R. and Potter, I. C. (2017), Optimization of foraging and diet by the piscivorous Othos dentex (Serranidae). J Fish Biol, 90: 1823–1841.
- ^ Gomon, M. F., Glover, J. C. M. & Kuiter, R. H. (2008). Fishes of Australia’s South Coast. Sydney: Reed New Holland
- ^ Kodric-Brown, A. (1998). Sexual dichromatism and temporary color changes in the reproduction of fishes. American Zoologist 38, 70–81.
- ^ a b Mank, J. E. (2007). The evolution of sexually traits and antagonistic androgen expression in actinopterygian fishes. American Naturalist 169, 143–149
- ^ a b c Bryars, S. & Shepherd, S. A. (2013). Ambush predators and night stalkers. Harlequin fish Othos dentex (Family Serranidae). In Ecology of Australian Temperate Reefs (Shepherd, S. & Edgar, G., eds), pp. 399–400. Collingwood: CSIRO Publishing
- ^ Saunders, R. J., Bryars, S. R. & Fowler, A. J. (2010). Preliminary consideration of the biology of several of South Australia’s marine fish species that have conservation or management interest. Report to the Department of Environment and Heritage. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2009/000693-1. SARDI Research Report Series No. 426
- ^ Fishbase.se
- ^ Dianne J. Bray, 2011, Harlequin Fish, Othos dentex, in Fishes of Australia, retrieved Mar. 12, 2015, http://www.fishesofaustralia.net.au/Home/species/4383
- ^ Platell, M. E., Hesp, S. A., Cossington, S. M., Lek, E., Moore, S. E. & Potter, I. C. (2010). Influence of selected factors on the dietary compositions of three targeted and co-occurring temperate species of reef fishes: implications for food partitioning. Journal of Fish Biology 76, 1255–1276.
- ^ Hunter, J. R., Lo, N. C. H. & Leong, R. J. H. (1985). Batch fecundity in multiple spawning fishes. In An Egg Production Method for Estimating Spawning Biomass of Pelagic Fish: Application to the Northern Anchovy, Engraulis mordax (Lasker, R. ed.), pp.66–78. NOAA NMFS Technical Report 36.
- ^ Erisman, B. E., Craig, M. T. & Hastings, P. A. (2009). A phylogenetic test of the size advantage model: evolutionary changes in mating behaviour influence the loss of sex change in a fish lineage. American Naturalist 174, 83–99.
- ^ Molloy, P. P., Goodwin, N. B., Cˆot´e, I. M., Reynolds, J. D. & Gage, M. J. G. (2007). Sperm competition and sex change a comparative analysis across fishes. Evolution 61, 640–652.
- ^ McEvoy, L. A. & McEvoy, J. (1992). Multiple spawning in several commercial fish species and its consequences for fisheries management, cultivation and experimentation. Journal of Fish Biology 41, 125–136.
- ^ Gerking, S. D. (1994). Feeding Ecology of Fish. London: Academic Press.
- ^ Gibran, F. Z. (2007). Activity, habitat use, feeding behaviour and diet of four sympatric species of Serranidae (Actinopterygii: Perciformes) in southeastern Brazil. Neotropical Ichthyology 5, 387–398.
- Froese, Rainer; Pauly, Daniel (eds.). "Othos Othos". FishBase.